Also Read: Antimicrobial Products Effectiveness Study

Proper use of antimicrobial coatings is the key to effective mold remediation within occupied buildings.

By Vern Batdorf and Fletcher Chambers

In the last few years the public has become increasingly aware of biological contamination in the occupied spaces where they live and work. The result has been a growing concern by the public, which has in turn resulted in a huge increase in sales of indoor air quality (IAQ) services and products. IAQ problem sources can be many. Since at least 50 percent of the problems have been attributed to the air handling system/ventilation system, the predominant use of disinfectants and antimicrobial coatings has, up to now, been on the interior of these air-handling systems. However, opportunities abound for the use of IAQ coatings to solve many other building microbial problems. The scope of antimicrobial coatings is expanding to include all potential growth areas within occupied structures that are susceptible to moisture problems.

The New Market

Every year, thousands of buildings are damaged by water, whether it comes from floods, hurricanes, frozen or broken water pipes, building leaks, or water damage from firefighting. Whenever you have moisture and a food source, mold can start to grow and spread within 24 to 48 hours, and will then grow exponentially given the right conditions of temperature, moisture, and food sources. Most building construction materials are excellent sources of food for mold, including dry wall, ceiling tiles, plywood, fiberboard and particleboard. Wall cavities are ideal areas for mold to grow once moisture accumulates either from water damage or condensation on the interior wall cavity.

Lack of sunlight, stagnant air, relative humidity above 60 percent and nutrients from the wood and dust in the wall cavity are all factors promoting mold growth, along with moisture or water from condensation. Mold can even be found on basement walls where the relative humidity is typically high and the temperature is above 70 degrees F. Bear in mind that mold spores and mold growth may be present and contribute to IAQ problems, even if they aren't visible to the naked eye.

One of the best ways to fight mold contamination is to prevent it from ever happening. Getting rid of water and humidity and drying up the space is one way. Also, antimicrobial coatings can be used to great advantage for mold prevention by applying them during construction or renovation. By applying an antimicrobial coating to the interior wall cavities before they're finished, even to floor joists and ceiling rafters, you can eliminate most nutrient sources for mold growth when and if moisture does accumulate in the building in the future. Since these coatings are typically water base, the temperature needs to be above 40 degrees F and stable during the application and drying stages.

When remediation work is being done in water-damaged buildings, it needs to be started quickly, since mold growth can commence 24 to 48 hours after being wet. For remediation work, application of disinfectants and coatings should be completed when the occupants aren't in the buildings, or when work areas are sealed off to isolate the occupants from the area.

Clean, Kill, and Prevent

Similar procedures apply for building surfaces as those in air handling systems. Again, it's clean, kill, and then protect. Surfaces must be completely cleaned to remove all mold and surface contamination down to a sound non-friable surface. Then, a suitable Environmental Protection Agency (EPA) registered disinfectant/cleaner should be spray applied to kill any remaining mold spores.

Wherever there is mold, mold damage or contaminated building materials such as wallboard, you must keep removing the mold and damaged materials until it's completely gone, either on exposed surfaces, or in enclosed spaces such as the backside of the sheetrock next to the studs. Any damaged material that has been removed and can't be cleaned should be bagged and sealed in plastic. The wall studs or floor joists may also have mold contamination, and you must consider how to inspect and treat the hidden surfaces such as the edge of the stud facing the exterior wall. Clean and salvage materials that aren't severely affected. Clean with powdered automatic dishwasher detergent and hot water. Gently wipe with a sponge or spray with a mist bottle. Also, repair and replace the removed material and dry out the area.

Once all surfaces have been cleaned, disinfected or removed, an antimicrobial coating can be applied. This is best done by electric airless spray application to completely cover all surfaces, corners and crevices. For long-term effectiveness, you should insure that the coating is designed to properly bond to the surface. In some cases such as metal or masonry surfaces, primer should be used to insure this bond. John Lausevic is vice president of Pacific Gold Coast Construction, Inc. (PGCC), a California based contracting firm specializing in bioremedial construction.

According to Lausevic, "Primers are critical. When applying the coating to an incompatible surface, delamination of the coating can be a problem. Using an appropriate primer for the job can solve this problem. "

Thickness is another critical factor in the success of antimicrobial coatings. Sufficient coating must be applied to adequately protect the surface for the life of the building. Skimping on material or thinning the product will result in subpar performance. The protection obtained is only as good as the dry film thickness of the coating.

Jay Colburn, president of Environmental Restoration in North Carolina, a contracting company that specializes in IAQ property restoration, has years of experience with antimicrobial coatings. He uses a "disciplined methodology" for maximum results from a coating.

"Thorough cleaning and complete source removal will provide the best surface possible for the coating," says Colburn. "If you do not provide the ideal bonding surface and appropriate coverage, your coating cannot give you ideal performance."

In many building areas, where high humidity is regularly present, mold can also be found growing on the interior finished surfaces of walls and ceilings. Some examples of these include school locker/shower rooms, laundry areas, shower rooms, swimming pool enclosures and even ice-skating rinks. Here again, the procedure is to clean, kill, and protect. One difference in these cases is that the coating must provide a finished surface that's both attractive and durable. It has to look good, but also be cleanable and abuse resistant.

Insure Effectiveness

In recent years the IAQ marketplace has seen many new products claiming to prevent mold growth or to disinfect surfaces. Care must be exercised in choosing disinfectant or antimicrobial coating, to assure that it's suitable for the intended purpose, and will meet all of your requirements. Some approaches to disinfecting, such as gassing the area with ozone or chlorine dioxide, can be hazardous and even life threatening.

Contractors also need to recognize that some state and local codes require remediation contractors to be licensed pesticide applicators before they can apply disinfectants and antimicrobial coatings. A contractor doesn't need to use a hazardous product to eliminate another hazard. There are a number of good and proven products in the marketplace that can be used safely when directions are followed. Unfortunately, there are also products in the marketplace that may mislead the purchaser regarding their benefit in preventing mold growth.

The best IAQ solution is to use only EPA registered disinfectants and coatings. These products have been proven to the EPA to be both effective and safe to use. Since the EPA regulates all labeling and data, a contractor and owner can trust product claims, directions, and cautions to be true and accurate. These products, when used as directed, are dependable and should perform as expected.

IAQ building problems offer great opportunities for professionals to come in and address the situation with the help of antimicrobial coatings and disinfectants. Mold and mildew present serious problems to both the structural integrity of a building and its occupants' health. By an effective use of these products as restorative measures in remediation projects, as well as preventive measures in new construction, the hazards of mold contamination can be abated.

In the fall 2000 issue of Risk Watch, a periodic survey published by the International Center for Toxicology and Medicine (ICTM), 54 percent of the group of owners and managers of commercial office space agreed that "growing public and regulatory concern about indoor air quality will likely lead to significant changes in building design and construction within the next five years." Antimicrobial coatings, which found their initial use in air handling system applications, can and will be a part of the solution of this growing concern.